The present invention relates to nucleoside 5'-alkyl- or alkenylphosphates which are novel derivatives of nucleosides having antiviral activity.
9-.beta.-D-Arabinofuranosylpurine and 1-.beta.-D-arabinofuranosylpyrimidine and their derivatives are known to exhibit high antiviral activity, and the commercial production of some of these compounds in the form of antiviral agents has been under development in recent years. Most of the data on the antiviral activity of arabinonucleosides heretofore reported has mainly related to the activity, for example, against herpes-simplex virus which is a DNA virus. Recently, 9-.beta.-D-arabinofuranosyladenine has been reported to have activity against hepetitis virus, and other arabinonucleosides are expected to become effective remedies for viral hepatitis.